A prion is a misshapen protein that acts like an infectious agent (hence the name, which comes from the words protein and infection).

Prions cause a number of fatal diseases such as mad cow disease in cattle, scrapie in sheep and kuru and Creutzfeldt-Jakob disease (CJD) in humans. There is no cure and potential treatments are highly speculative.

In recent years, however, biologists have discovered several animals that are immune to prion diseases. These include horses, dogs and rabbits. Nobody knows why.

But a great deal of effort is being expended to find out. In the last couple of years, molecular biologists have identified the structure of the proteins in these immune species that in other animals cause prion disease. The obvious question is this: what’s the difference?

Today, we have an answer thanks to an impressive set of molecular simulations carried out by Jiapu Zhang at the The University of Ballarat in Australia.

Zhang has simulated how these proteins change shape as their temperature and pH changes.

His conclusion is that the immune proteins are more stable than the others because of a salt bridge that connects two parts of the immune proteins “like a taught bow string”. This prevents them from misfolding into an infectious form.

That’s an interesting result because it immediately provides a therapeutic target to aim at. “This salt bridge might be a potential drug target for prion diseases,” says Zhang.

The idea is that it might be possible to stabilise prion proteins in cattle, sheep and humans using an artificial salt bridge, similar to the one in dogs, horses and rabbits.

A long shot but certainly worth pursuing.

Ref: arxiv.org/abs/1106.4628: The Nature Of The Infectious Agents: PrP Models Of Resistant Species To Prion Diseases (Dog, Rabbit And Horses)